1. Field of the Invention
An aspect of the present invention relates to at least one of a magnetic body composition and a magnetic body product.
2. Description of the Related Art
Many information associated instruments or systems function along with development of information techniques and many of such instruments or systems are operated by digital signals, so that a problem may be that a variety of interference between instruments or devices generated by electromagnetic wave noise causes malfunction thereof. In order to address such a problem, while it may be necessary to suppress undesired electromagnetic wave radiation as may influence on an operation of an individual instrument or device per se or an operation of another instrument or device, it may be necessary to have durability so as not to break down against electromagnetic wave noise (an approaching electromagnetic wave) from an exterior. Thus, it is known that an electromagnetic wave absorbing body that contains a magnetic material, electromagnetic wave absorbing sheet, or the like is used as a countermeasure against electromagnetic wave noise.
In recent years, a nanometer size magnetic material that is expected to develop a specific magnetic characteristic (for example, superparamagnetism, magnetoresistance effect, magnetic anisotropy, or the like) is drawing attention and is being studied. For a nanometer size magnetic material, for example, a method has been proposed for manufacturing a metal magnetic powder for magnetic recording with a particle length greater than or equal to 10 nm and less than or equal to 45 nm and an axis ratio greater than or equal to 2) by applying a reducing agent to a metal magnetic powder that has a metal magnetic phase based on Fe or Fe and Co and contains a non-magnetic component (one or more kinds of Al and Si) in a fluid that contains a complexing agent capable of forming a complex with at least one or more kinds of non-magnetic components (see Japanese Patent Application Publication No. 2008-270300 (Japanese Patent No. 4758936)).
Furthermore, a method has been proposed for forming ferromagnetic nanoparticles by a step of forming a metal precursor solution from a transition metal, a step of adding the metal precursor solution into a surfactant solution, a step of precipitating nanoparticles from the solution by addition of a coagulant without causing permanent coagulation thereof, and a step of conducting recombination or colloid reproduction of the nanoparticles by addition of a hydrocarbon solvent (see U.S. Pat. No. 6,162,532).
Furthermore, a method has been proposed for stabilizing a layered periodic array that is composed of magnetic nanoparticles in a magnetic storage medium wherein the array is formed on a substrate surface (see Japanese Patent Application Publication No. 2000-48340). The magnetic nanoparticles are formed of a magnetic material selected from a group composed of Co, Fe, Ni, Mn, Sm, Nd, Pr, Pt, and Gd elements, intermetallic compounds of the elements, binary alloys of the elements, ternary alloys of the elements, Fe oxides that further include at least one of the elements other than Fe, barium ferrite, and strontium ferrite.
Furthermore, in order to address a need of thinning of a magnetic recording layer as is necessitated to improve a higher output characteristic of a magnetic recording medium, it has been proposed that a non-magnetic underlayer that contains hematite powder is provided on a base film to smooth a surface thereof (see Japanese Patent Application Publication No. 2002-255560 (Japanese Patent No. 3763353)). The hematite powder is an aggregate that has a structure in such a manner that needle hematite particles with an average long axis diameter of 0.005-0.3 μm and an average short axis diameter of 0.0005-0.10 μm are directionally arrayed in a long axis direction.
A feature that determines a magnetic property of nanoparticles is present in a shape thereof. For example, one of conditions involved in magnetically anisotropic energy is isotropy or anisotropy that is greater for an elongated particle than for a spherical particle. Hence, it may be desirable to develop a method for producing particles that have different shapes, or in particular, elongated shapes. That is, one of essential conditions for producing a magnetic particle optimized for such a purpose is present in controlling of a size, size distribution, and shape thereof, and a problem may be that if it is not possible to control a distribution condition, a magnetic body formed by coating or the like may be basically non-uniform and it may not be possible to provide a functionality well.
On the other hand, for a conventional nanometer size magnetic material with an anisotropic shape that has a long axis and a short axis, a problem may be that a magnetic permeability thereof may be lower at a higher frequency. For example, for a needle hematite particle (that has a long axis greater than or equal to 100 nm and a short axis around 20 nm) as described in Japanese Patent Application Publication No. 2002-255560 (Japanese Patent No. 3763353), the magnetic permeability thereof at a higher frequency greater than or equal to 1 GHz is a lower value less than or equal to 1 H/m. Accordingly, it may be difficult to be used as an electromagnetic wave absorbing material for an electronic instrument or device used in a higher frequency domain greater than or equal to 1 GHz (for example, an RF instrument or a UHF instrument).
Additionally, a semiconductor component, a circuit board, and the like are known as the electronic instrument or device. For example, for a circuit board, an RF circuit has been proposed wherein a circuit for processing a radio frequency signal is formed on a dielectric substrate that has a meta-substance area (meta-substance: a substance formed by compounding two or more substances mixed or arranged at an extremely fine level such as a molecule or nanometer) that has a locally selective magnetic permeability and a substrate characteristic (see Japanese Patent Application Publication No. 2007-048736).
Furthermore, for a material for sealing a semiconductor component, a sealing resin composition has been proposed where 0.3-1.0 weight % of a carbon black with an average particle diameter of 20-40 nm per 100 weight % of the sealing resin composition is contained in a resin based on an epoxy resin base compound, a curing agent, and an accelerating agent (see Japanese Patent Application Publication No. 2000-273288). Thereby, it may be possible to obtain a sealing resin composition that has both an insulating property and a light blocking property.
As described above, problems may be that a ratio of a long axis to a short axis of a magnetic body may be greater than or equal to 2 in a conventional nanometer size magnetic material with an anisotropic shape that has a long axis and a short axis (Japanese Patent Application Publication No. 2008-270300 (Japanese Patent No. 4758936)) and a magnetic permeability at a higher frequency may be lower in Japanese Patent Application Publication No. 2002-255560 (Japanese Patent No. 3763353) (wherein a long axis is greater than or equal to 100 nm and a short axis is around 20 nm). For example, a needle hematite particle described in Japanese Patent Application Publication No. 2002-255560 (Japanese Patent No. 3763353) has a magnetic permeability at a higher frequency greater than or equal to 1 GHz that is a lower value less than or equal to 1 H/m. Additionally, although the magnetic permeability is expressed as a real term and ideal term separately, the magnetic permeability presented in an embodiment of the present invention refers to a real part of a complex magnetic permeability and a unit thereof is H/m.
Because the magnetic permeability of nanometer size magnetic material with an anisotropic shape at a higher frequency may be lower, it may be difficult to be used as a magnetic wave absorbing material for an electronic instrument or device used in a higher frequency domain greater than or equal to 1 GHz (for example, a digital camera, a mobile phone, a microprocessor or LSI for a notebook personal computer, or a UHF instrument or RF instrument such as a liquid crystal panel). Furthermore, although a variety of magnetic materials that contain nanometer size magnetic materials (nanoparticles) and have electromagnetic wave absorbing capabilities are being studied, a problem may be that it may be difficult to control sizes, a size distribution, and shapes of nanoparticles, and when, for example, forming due to coating or the like is conducted by using a forming material that includes such nanoparticles, a magnetic body may be non-uniform so that it may not be possible to exert functionality thereof sufficiently.